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Nerve root wiggle room

 •  • by Paul Ingraham
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Weekly nuggets of pain science news and insight, usually 100-300 words, with the occasional longer post. The blog is the “director’s commentary” on the core content of a library of major articles and books about common painful problems and popular treatments. See the blog archives or updates for the whole site.

Funny how tricky it can be to find a citation to confirm something relatively obvious. In this case, I’ve been aware for many years that nerve roots have a lot of “wiggle room” where they pass through their holes in the spine. This is a useful fact for reassuring people that “nerve pinches” are unusual. It’s come up in my reading many times over the years, and I’ve seen many anatomical drawings and dissection videos and so on, but … citation needed, right? I try to check all my assumptions.

When I set to “proving” what I know with a citation to a scientific paper, I had some trouble! It was hard data to find for some reason, and the paper I finally found, Torun et al kicks off by confirming that impression: “There have been few anatomic studies on the foramina and roots of the lumbar region … .” Indeed. And that’s in a 2006 paper! Hardly ancient.

However, what I knew was confirmed. The holes between the (lumbar) vertebrae that the nerve roots pass through can be more than a couple centimetres wide, while the nerve roots themselves are only about 3-4mm thick. I made a diagram:

Schematic of nerve root wiggle room

On the left are the rough proportions of a healthy nerve root and the hole it passes through (intervertebral foramen). I also found some simple data on how the holes change shape during spinal traction and compression (Sari et al, Takasaki et al): they get a little larger or smaller, as shown on the right … but there’s still lots of nerve root room.

I’ve added these references to three books (low back pain, neck pain, trigger points), plus an excerpt, Nerve Pain Is Overdiagnosed.